The vision of ubiquitous computing in interactive mobile cloud applications and Internet of Things (IoT) based systems is still difficult to achieve. The difficulty lies in the use of cloud services in mobile devices, which impacts the issues of performance, scalability, availability, and lack of resources in mobile computing environments. Despite the astonishing advancement achieved in IoT technology, there is still much to do. Some IoT-based systems, which rely on a variety of mobile devices, need to work even when the connection is temporarily unavailable or under-degraded. Besides, mobile cloud service providers can reduce network latency by moving some of their services close to the user. To cope with this challenge, we propose in this chapter the usage of small clouds known as cloudlets, and we describe two cloudletbased architectures, which allow leveraging the geographical proximity of cloud services to mobile users. We model the network latency of the different components of the two architectures using a continuous-time Markov chain (CTMC). These components are essentially the user nodes, the cloudlets, and the principal cloud. For each architecture, we simulate queries submitted by mobile users to a search engine, and we estimate the incurred delay by using the CTMC state models.

Chapter Contents:

4.1 Introduction

4.2 Related work

4.3 Cloudlet architectures

4.3.1 Hierarchical architecture

4.3.1.1 Formulation of latency delay for one request

4.3.1.2 Formulation of the latency delay for multiple requests submission

4.3.2 Ring architecture

4.3.2.1 Formulation of the latency delay for multiple requests submission